The present invention relates to a wafer transfer system and method, and an automatic guided vehicle system having a transfer unit wherein arms for transferring the wafers are provided on a turntable, an orientation unit which adjusts the orientation and direction of the wafers set on a place table and a reading unit which reads an ID put in the wafer side by side. For example, the wafer transfer system is loaded in an automatic guided vehicle which carries and transfers the wafers automatically between stations in a semiconductor manufacturing plant.
So far, the orientation unit is operated for putting the wafer in the predetermined position and orientation to the transfer unit for reading the ID information put in the wafer by an OCR and the transfer unit sets the wafer to the OCR.
More specifically, the positioning unit comprises a move table which can move to two axel which cross on a horizontal plane and a turnable place table disposed on it, and this orientation unit turns the place table with placing the wafer on it, an orientation flat position (or a notch position) of the wafer is detected by a sensor and a peripheral turn track of the measured wafer is compared with a basic turn track memorized in advance, so that the difference between the central position in the wafer and the basic position is calculated, and the place table is turned for putting the wafer in the predetermined orientation and the move table is moved such that the center of the wafer is placed on the predetermined position based on this calculation result. Thus, as the wafer can be moved to an area where the OCR can read the ID mark in the correct and proper orientation when the position and orientation of the wafer are adjusted in advance, the OCR can read the ID mark without failing.
The above transfer unit needs a move table which can move the wafers horizontally with high accuracy and it also takes time to move the wafer. Consequently, it is an object of the present invention to eliminate this move table, to reduce time for orienting the wafer and to improve transfer efficiency of the wafer.
The problem to be solved by the present invention is described above, and a means for solving the problem will be described next.
First, a wafer transfer system having a transfer unit wherein arms for transferring wafers are provided on a turntable, an orientation unit which adjusts the orientation and direction of the wafer set on a place table and a reading unit which reads an ID mark put in a wafer, is provided with a calculation means which calculates a central position of the wafer set on the place table, a turn angle calculation means for calculating a turn angle for the wafer to be in a predetermined orientation based on a calculation result of the calculation means and positional information of the ID mark received in advance, a transfer quantity calculation means which calculates a quantity of expanding and contracting the arm in the transfer unit and a turn angle of the turntable necessary for setting the wafer in the predetermined orientation such that the ID mark comes to a predetermined position and orientation to the reading unit and a correction means which corrects the turn angle of the place table calculated by the turn angle calculation means based on the turn angle of the turntable calculated by the transfer quantity calculation means.
Additionally, regarding a wafer transfer method having a transfer unit wherein arms for transferring wafers are provided on a turntable, an orientation unit which adjusts the orientation and direction of the wafer set on a place table and the reading unit which reads the ID mark put in the wafer, a central position of the wafer set on the place table is calculated, a turn angle of the place table that the wafer comes to a predetermined orientation is calculated based on the calculated central position of the wafer and positional information of the ID mark received in advance, a quantity of expanding and contracting the arm and a turn angle of the turntable in the transfer unit necessary for setting the wafer in a predetermined orientation such that the ID mark comes to a predetermined position and orientation to the reading unit are calculated, the calculated turn angle of the place table is corrected based on the calculated turn angle of the turntable, the place table is turned only by the turn angle after correcting and the wafer is turned, the turned wafer is moved to the reading unit side by the transfer unit and the wafer is set such that the ID mark is in the predetermined position and orientation to the reading unit.
Furthermore, the wafer transfer system as described in claim 1 is provided with the automatic guided vehicle in the automatic guided vehicle system comprising an automatic guided vehicle having a transfer unit wherein arms for transferring the wafers are provided on a turntable, an orientation unit which adjusts the orientation and direction of the wafer set on the place table and a reading unit which reads the ID mark put in the wafer.